The parking brake/springs brake automatically engages at___-to____psi

The parking brake/springs brake automatically engages at___-to____psi

• A. 5-15
• B. 60-75
• C. 80-100
• D. 20-45

Answer: (D)

Spring-applied, air-released parking brakes are held off by system pressure, and when that pressure drops to a low threshold, the release springs snap the brakes on. That threshold is typically around 20 to 45 psi. Keeping the engagement point in this low range ensures the parking brake automatically activates if the air pressure bleeds down, preventing the vehicle from moving unintentionally. The other ranges would either be above the point at which the brakes are designed to engage or far below what the system can reliably sense, making them incorrect for automatic engagement.

Spring-applied, air-released parking brakes are held off by system pressure, and when that pressure drops to a low threshold, the release springs snap the brakes on. That threshold is typically around 20 to 45 psi. Keeping the engagement point in this low range ensures the parking brake automatically activates if the air pressure bleeds down, preventing the vehicle from moving unintentionally. The other ranges would either be above the point at which the brakes are designed to engage or far below what the system can reliably sense, making them incorrect for automatic engagement.